How an Exchange Server Stores Data

Exchange servers store data as two separate
files:

an .edb file

an .stm file

Together, the .edb file and the .stm file
form an Exchange store repository. The .edb and .stm files
function as a pair, and the database signature (a 32-bit random
number combined with the time that the database was created)
is stored as a header in both files. The internal schema for
the .stm pages is stored in the .edb file. It is important
to understand that a single database in the Exchange Server
Information Store service contains two files, the .edb file
and the .stm file. One of these files is of little use without
the other file. The traditional .edb file and its accompanying
.stm file are a single unit.

The .edb file contains many tables that
hold metadata for all e-mail messages and other items in the
Exchange store, in addition to the contents of MAPI messages.
The .edb file is an ESE database, and because it is used primarily
to store MAPI messages and attachments, it is also referred
to as the MAPI-based database.

The .stm file, in contrast, stores native
Internet content. Because Internet content is written in native
format, there isn’t a need to convert messages and other
items to Exchange format. The .stm file is also an ESE database,
referred to as the streaming database.

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